"Service 4WD" Message '05 Silverado

[sdailey]

Need some input folks. Earlier this week my truck threw up this message on my dash and it has not gone away. The truck has push button 4wd and with this message up I can't engage 4wd at all. Is there anything in particular to look for? I have not tried disconnecting the battery yet. I'm not sure if that "trick" still works on newer vehicles or not. The truck sees very limited 4wd use and has roughly 80k miles on it.

Any ideas on what may be wrong?

Thanks in advance.